Design and implementation of a MAC controller for the IEEE802.11 wireless LAN

IEEE 802.11 wireless LANs have a tremendous market potential, as they support high data rates, work in the world-wide licence free 2.4 GHz ISM band and have high performance in terms of range and power consumption. Hence, the development of a communication processor that supports the IEEE 802.11 MAC functions has a significant potential, making very important the concept of having an ASIC ‘right from the first time’, in order to minimize development cost and to meet short time-to-market requirements. This paper presents the methodology of developing such a component with emphasis on the rapid prototyping approach. The chip architecture, which is based on an ARM processor core, is described in detail, focusing on the implementation of the protocol functions using custom hardware modules. Finally, the paper presents experimental results on the ASIC implementation.     

A new threshold‐voltage compensation technique of poly‐Si TFTs for AMOLED display pixel circuits

Abstract— A new threshold‐voltage compensation technique for polycrystal line‐silicon thin‐film transistors (poly‐Si TFTs) used in active‐matrix organic light‐emitting‐diode (AMOLED) display pixel circuits is presented. The new technique was applied to a conventional 2‐transistor—1‐capacitor (2T1C) pixel circuit, and a new voltage‐programmed pixel circuit (VPPC) is proposed. Theoretically, the proposed pixel is the fastest pixel with threshold‐voltage compensation reported in the literature because of the new compression technique implemented with a static circuit block, which does not affect the response time of the conventional 2T1C pixel circuit. Furthermore, the new pixel exhibits all the other advantages of the 2T1C pixel, such as the simplicity of the peripheral drivers and improves other characteristics, such as its behavior in the temperature variations. The verification of the proposed pixel is made through simulations with HSpice. In order to obtain realistic simulations, device parameters were extracted from fabricated low‐temperature poly‐Si (LTPS) TFTs.     

A New Analog Buffer Using Low-Temperature Polysilicon Thin-Film Transistors for Active-Matrix Displays

In this paper, a new source-follower-type analog buffer for active-matrix displays, designed by using low-temperature polysilicon thin-film transistors (TFTs), is proposed. The buffer, consisting of five n-type polysilicon TFTs, one bias voltage, and an additional control signal, exhibits high immunity to threshold voltage and mobility variations. The functionality of the proposed buffer was verified by HSPICE simulations. In order to obtain realistic simulations, the TFT model parameters used for the simulations were extracted from fabricated TFTs using the Silvaco tools (ATLAS). The proposed buffer has 7-bit output voltage with the dynamic output voltage range of 7.5 V ranging from 2.5 to 10 V and with resolution up to 0.03 V     

Model catalyst studies with single crystals and epitaxial thin oxide films

The paper describes recent results from our relatively new program to perform detailed studies of the catalytic properties of metal-oxide materials; in particular, to effect a determination of the active catalytic site(s) and the mechanism for reactions over this especially important class of heterogeneous catalysts. Issues of structure-sensitivity, poisoning and promotion, and competing reaction mechanisms are critical questions that need to be addressed in a detailed manner for catalysis by oxides. As just one important example, both surface (Langmui–Hinshelwood) and direct (Eley–Rideal) reaction mechanisms have been proposed for the selective catalytic reduction (SCR) reaction of nitrogen oxides (NO_x) over vanadia/titania catalysts. For this program, we are using a number of unique, state-of-the-art capabilities available in the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory; for example, the first molecular beam epitaxy (MBE) system dedicated to the growth of model metal-oxide films, and a unique moderate-pressure catalytic reactor/surface science apparatus. We describe the growth, characterization, and water adsorption properties of a thin Fe₃O₄(0 0 1) film grown on a lattice-matched MgO(0 0 1) substrate. Because our moderate pressure catalysis studies are preliminary at this point, we instead describe our previous results on the CO oxidation reaction over a Ru(0 0 0 1) model catalyst to demonstrate the utility of the experimental approach. We specifically discuss the possibility that this reaction occurs by an Eley–Rideal mechanism.     

Transforming communicating X-machines into P systems

Tissue P systems (tPS) represent a class of P systems in which cells are arranged in a graph rather than a hierarchical structure. On the other hand, communicating X-machines (XMs) are state-based machines, extended with a memory structure and transition functions instead of simple inputs, which communicate via message passing. One could use communicating XMs to create models built out of components in a rather intuitive way. There are investigations showing how various classes of P systems can be modelled as communicating XMs. In this paper, we define a set of principles to transform communicating XMs into tPS. We describe the rules that govern such transformations, present an example to demonstrate the feasibility of this approach and discuss ways to extend it to more general models, such as population P systems, which involve dynamic structures.     

Importance of intercostal artery reattachment during thoracoabdominal aortic aneurysm repair

PURPOSE: We studied the relationship of neurologic deficit to ligation, reimplantation, and preexisting occlusion of intercostal arteries to determine which arteries and consequent management are most critical to outcome in thoracoabdominal aortic aneurysm repair. METHODS: From February 1991 to July 1996, 343 patients with thoracoabdominal aortic aneurysms underwent repair by one surgeon. In this study, only Crawford types I, II, and III (n = 264) were considered. Of these, 110 (42%) were type I, 116 (44%) type II, and 38 (14%) type III. The adjuncts of distal aortic perfusion and cerebrospinal fluid drainage were used in 164 patients (62%). Data were analyzed by contingency table and by multiple logistic regression. RESULTS: Early neurologic deficit occurred in 23 patients (8.7%), and late deficit in 10 patients (3.8%). Neurologic deficit in patients with at least one reimplantation and no ligation of arteries T11 or T12 occurred in 19 of 147 (12.9%). Neurologic deficit for occlusion of the same arteries occurred in 11 of 111 (9.9%), whereas for ligation of T11 and T12 neurologic deficit occurred in three of six (50%; reimplantation, p < 0.03; occlusion, p < 0.006). In addition, reimplantation of intercostal arteries T9 or T10 was significantly associated with reduced late neurologic deficit in multivariate analysis (p = 0.05). No other intercostal artery status was associated with modification of the neurologic deficit rate. Multivariate analysis showed type II aneurysms and acute dissections to be significantly associated with an increased risk of postoperative neurologic deficit (p < 0.0009, 0.002, respectively). Adjuncts were protective (p < 0.007), most often in types II and III (14.1% neurologic deficit in type II with adjunct, 35.3% without; 0% in type III with adjunct, 20% without). CONCLUSION: Patients with patent arteries at the T11/T12 level have highly variable outcomes depending on whether the arteries are reattached or ligated. Our data suggest that reimplantation of thoracic intercostal arteries T11 and T12 is indicated when these arteries are patent. Reimplantation of T9 and T10 lowers the risk of late neurologic deficit, probably by decreasing the spinal cord's vulnerability to changes in blood and cerebrospinal fluid pressure in the days after surgery. Adjuncts lower overall risk and provide adequate time for targeted intercostal artery reimplantation.     

Characterization of KC60Obtained via a Potassium Carbonate Route

KC_6o synthesized by high temperature annealing of mixture of C₆₀ and K₂C0₃has been characterized by EPR, NMR and differential scanning calorimetry methods. The rich phase diagram with polymeric and dimer phases previously elaborated for KC₆₀ is obtained in present work as well. This suggests that alkaline carbonates can be efficiently used in preparation of C₆₀-based polymer materials where C_6o molecules are charged by alkaline atoms. Another important outcome of present study is that despite high temperatures and presence of oxygen released from K₂CO₃, EPR and NMR spectra did not exhibit signals which might be referred to fullerene epoxides or related species.